org.apache.commons.logging.impl

Class LogFactoryImpl


public class LogFactoryImpl
extends LogFactory

Concrete subclass of LogFactory that implements the following algorithm to dynamically select a logging implementation class to instantiate a wrapper for.

If the selected Log implementation class has a setLogFactory() method that accepts a LogFactory parameter, this method will be called on each newly created instance to identify the associated factory. This makes factory configuration attributes available to the Log instance, if it so desires.

This factory will remember previously created Log instances for the same name, and will return them on repeated requests to the getInstance() method. This implementation ignores any configured attributes.

Version:
$Revision: 1.33 $ $Date: 2004/03/06 21:52:59 $
Authors:
Rod Waldhoff
Craig R. McClanahan
Richard A. Sitze

Field Summary

private static String
LOG_INTERFACE
The name of the Log interface class.
static String
LOG_PROPERTY
The name of the system property identifying our Log implementation class.
protected static String
LOG_PROPERTY_OLD
The deprecated system property used for backwards compatibility with the old LogSource class.
protected Hashtable
attributes
Configuration attributes.
protected Hashtable
instances
The Log instances that have already been created, keyed by logger name.
private String
logClassName
Name of the class implementing the Log interface.
protected Constructor
logConstructor
The one-argument constructor of the Log implementation class that will be used to create new instances.
protected Class[]
logConstructorSignature
The signature of the Constructor to be used.
protected Method
logMethod
The one-argument setLogFactory method of the selected Log method, if it exists.
protected Class[]
logMethodSignature
The signature of the setLogFactory method to be used.

Fields inherited from class org.apache.commons.logging.LogFactory

FACTORY_DEFAULT, FACTORY_PROPERTIES, FACTORY_PROPERTY, SERVICE_ID, factories

Constructor Summary

LogFactoryImpl()
Public no-arguments constructor required by the lookup mechanism.

Method Summary

Object
getAttribute(String name)
Return the configuration attribute with the specified name (if any), or null if there is no such attribute.
String[]
getAttributeNames()
Return an array containing the names of all currently defined configuration attributes.
Log
getInstance(Class clazz)
Convenience method to derive a name from the specified class and call getInstance(String) with it.
Log
getInstance(String name)
Construct (if necessary) and return a Log instance, using the factory's current set of configuration attributes.
protected String
getLogClassName()
Return the fully qualified Java classname of the Log implementation we will be using.
protected Constructor
getLogConstructor()
Return the Constructor that can be called to instantiate new Log instances.
protected boolean
isJdk13LumberjackAvailable()
Is JDK 1.3 with Lumberjack logging available?
protected boolean
isJdk14Available()
Return true if JDK 1.4 or later logging is available.
protected boolean
isLog4JAvailable()
Is a Log4J implementation available?
private static Class
loadClass(String name)
MUST KEEP THIS METHOD PRIVATE.
protected Log
newInstance(String name)
Create and return a new Log instance for the specified name.
void
release()
Release any internal references to previously created Log instances returned by this factory.
void
removeAttribute(String name)
Remove any configuration attribute associated with the specified name.
void
setAttribute(String name, Object value)
Set the configuration attribute with the specified name.

Methods inherited from class org.apache.commons.logging.LogFactory

cacheFactory, getAttribute, getAttributeNames, getCachedFactory, getContextClassLoader, getFactory, getInstance, getInstance, getLog, getLog, getResourceAsStream, newFactory, release, release, releaseAll, removeAttribute, setAttribute

Field Details

LOG_INTERFACE

private static final String LOG_INTERFACE
The name of the Log interface class.

LOG_PROPERTY

public static final String LOG_PROPERTY

LOG_PROPERTY_OLD

protected static final String LOG_PROPERTY_OLD

attributes

protected Hashtable attributes
Configuration attributes.

instances

protected Hashtable instances
The Log instances that have already been created, keyed by logger name.

logClassName

private String logClassName
Name of the class implementing the Log interface.

logConstructor

protected Constructor logConstructor
The one-argument constructor of the Log implementation class that will be used to create new instances. This value is initialized by getLogConstructor(), and then returned repeatedly.

logConstructorSignature

protected Class[] logConstructorSignature
The signature of the Constructor to be used.

logMethod

protected Method logMethod

logMethodSignature

protected Class[] logMethodSignature
The signature of the setLogFactory method to be used.

Constructor Details

LogFactoryImpl

public LogFactoryImpl()
Public no-arguments constructor required by the lookup mechanism.

Method Details

getAttribute

public Object getAttribute(String name)
Return the configuration attribute with the specified name (if any), or null if there is no such attribute.
Overrides:
getAttribute in interface LogFactory
Parameters:
name - Name of the attribute to return

getAttributeNames

public String[] getAttributeNames()
Return an array containing the names of all currently defined configuration attributes. If there are no such attributes, a zero length array is returned.
Overrides:
getAttributeNames in interface LogFactory

getInstance

public Log getInstance(Class clazz)
            throws LogConfigurationException
Convenience method to derive a name from the specified class and call getInstance(String) with it.
Overrides:
getInstance in interface LogFactory
Parameters:
clazz - Class for which a suitable Log name will be derived
Throws:
LogConfigurationException - if a suitable Log instance cannot be returned

getInstance

public Log getInstance(String name)
            throws LogConfigurationException
Construct (if necessary) and return a Log instance, using the factory's current set of configuration attributes.

NOTE - Depending upon the implementation of the LogFactory you are using, the Log instance you are returned may or may not be local to the current application, and may or may not be returned again on a subsequent call with the same name argument.

Overrides:
getInstance in interface LogFactory
Parameters:
name - Logical name of the Log instance to be returned (the meaning of this name is only known to the underlying logging implementation that is being wrapped)
Throws:
LogConfigurationException - if a suitable Log instance cannot be returned

getLogClassName

protected String getLogClassName()

getLogConstructor

protected Constructor getLogConstructor()
            throws LogConfigurationException
Return the Constructor that can be called to instantiate new Log instances.

IMPLEMENTATION NOTE - Race conditions caused by calling this method from more than one thread are ignored, because the same Constructor instance will ultimately be derived in all circumstances.

Throws:
LogConfigurationException - if a suitable constructor cannot be returned

isJdk13LumberjackAvailable

protected boolean isJdk13LumberjackAvailable()
Is JDK 1.3 with Lumberjack logging available?

isJdk14Available

protected boolean isJdk14Available()
Return true if JDK 1.4 or later logging is available. Also checks that the Throwable class supports getStackTrace(), which is required by Jdk14Logger.

isLog4JAvailable

protected boolean isLog4JAvailable()
Is a Log4J implementation available?

loadClass

private static Class loadClass(String name)
            throws ClassNotFoundException
MUST KEEP THIS METHOD PRIVATE.

Exposing this method outside of org.apache.commons.logging.LogFactoryImpl will create a security violation: This method uses AccessController.doPrivileged(). Load a class, try first the thread class loader, and if it fails use the loader that loaded this class.


newInstance

protected Log newInstance(String name)
            throws LogConfigurationException
Create and return a new Log instance for the specified name.
Parameters:
name - Name of the new logger
Throws:
LogConfigurationException - if a new instance cannot be created

release

public void release()
Release any internal references to previously created Log instances returned by this factory. This is useful in environments like servlet containers, which implement application reloading by throwing away a ClassLoader. Dangling references to objects in that class loader would prevent garbage collection.
Overrides:
release in interface LogFactory

removeAttribute

public void removeAttribute(String name)
Remove any configuration attribute associated with the specified name. If there is no such attribute, no action is taken.
Overrides:
removeAttribute in interface LogFactory
Parameters:
name - Name of the attribute to remove

setAttribute

public void setAttribute(String name,
                         Object value)
Set the configuration attribute with the specified name. Calling this with a null value is equivalent to calling removeAttribute(name).
Overrides:
setAttribute in interface LogFactory
Parameters:
name - Name of the attribute to set
value - Value of the attribute to set, or null to remove any setting for this attribute

Copyright 2002-2004 The Apache Software Foundation.